Drive means for material compacting apparatus

ABSTRACT

A material compacting apparatus including opposed compacting rolls mounted for lateral displacement to vary the spacing between the rolls depending upon the pressure exerted during compacting. A hopper is positioned above the rolls for holding the material, and a feed screw is located within the hopper for feeding the material to the rolls. Control means are provided for varying the driving action of the feed screw with the variations depending upon any tendency of the pressure applied by the rolls to vary. The feed screw is hydraulically or electrically driven and signals are applied to the drive means for varying the feed screw pressure. Variations in the driving force of the feed screw are designed to offset the forces tending to vary the spacing between the rolls whereby a constant roll spacing, and therefore a product of constant thickness can be achieved.

Elite arris 1 May 22, 1973 541 DRIVE MEANS FOR MATERIAL 3,632,244 1 1972Sturgeon et al ..425 145 x COMPACTING APPARATUS [75] Inventor: Leroy S.Harris, Rolling Meadows, Primary ExaminerfiRobert L. Spicer Jr.

11L Attorney-McDougal, Hersh & Scott [73] Assignee: K-G Industries Inc.,Rosemont, Ill.

[22] Filed: Feb. 16, 1972 [57] ABSTRACT PP 226,824 A material compactingapparatus including opposed compacting rolls mounted for lateraldisplacement to Related f Apphcatlon Dam vary the spacing between therolls depending upon the [63] Continuation-in-part of Ser. No. 95,456,Dec. 7, pressure exerted during compacting. A hopper is posi- 1970, Pat.No. 3,674,397.

tioned above the rolls for holding the material, and a feed screw islocated within the hopper for feeding the material to the rolls. Controlmeans are provided for 425/78 varying the driving action of the feedscrew with the f 329C B299 variations depending upon any tendency of thepres- Fleld of Search 78, 367, sure the rolls to vary The feed crew is449 hydraulically or electrically driven and signals are applied to thedrive means for varying the feed screw References Cited pressure.Variations in the driving force of the feed UNITED STATES PATENTS screware designed to offset the forces tending to vary the spacing betweenthe rolls whereby a constant roll 3,450,529 6/1969 MacDonald 425/145 Xspacing, and therefore a product of constant thickness 3,111,707 11/1963Buckley ..425/145 can be achieved 3,320,905 5/1967 Urschel ..425/l453,277,218 10/1966 Dollinger ..425/ 145 X 5 Claims, 6 Drawing Figures A i10 I s I I ,f J.I h-

n I I c iilflwf 3 iq 1 L' I i 12 1 J L l l i i flfl 'll a I 1PATENTEUHAYZZW I 3.734.659

SHEET 3 OF 3 FIG, 6

DRIVE MEANS FOR MATERIAL COMPACTING APPARATUS RELATED APPLICATION Thisapplication is a continuation-in-part of applicants copendingapplication Ser. No. 95,456, now U.S. Pat. No. 3,674,397, filed on Dec.7, 1970.

This invention relates to an apparatus for compacting material. Inparticular, the invention is concerned with constructions such asbriquetting machines wherein material is continuously fed betweenopposed rolls. The rolls are driven at a specified rate whereby acontinuous length of compacted product will issue from between therolls.

Briquetting machines and other types of compacting equipment preferablyemploy compacting rolls which are laterally displaceable depending uponthe pressure between the rolls. Reference is made for example toKomarek, et al. U.S. Pat. No. 2,977,631 which illustrates anagglomerating construction having one compacting roll mounted forrotation on a stationary axis with an opposing compacting roll mountedin displaceable bearing blocks. Spring means normally urge thedisplaceable block to a specific position; however, if the pressurebetween the rolls exceeds the spring pressure, then the bearing blockswill yield whereby this pressure can be relieved.

Compacting constructions also preferably employ pressure feeding meansfor delivering the material to be compacted to the compacting rolls.Such screw feeding means are illustrated in the aforementioned patentand also in Komarek Pat. No. 3,269,611. By controlling the rate andpressure of material delivery to the compacting rolls, the uniformity ofthe resulting product can be controlled. U.S. Pat. No. 2,977,631discusses a control system for the feed screw providing means forcontrolling the rate of feed of the particulate material to the nip ofthe compacting rolls for purposes of providing varying feed pressuredepending upon the type of material being handled.

In applicants Scr. No. 95,456, an arrangement is described whereby thespacing between compacting rolls can be maintained at a substantiallyconstant distance through the use of means for detecting variations inroll pressure and controls for hydraulic feed screw drive means wherebyvariations in feed screw activity are accomplished in accordance withchanges in pressure being exerted by the rolls on the material beingcompacted. This application is directed to the same concept and alsorefers to control means for operating electrical drives whereby certainadvantages can be accomplished along with those referred in the previousapplication.

It is a general object of this invention to provide an improved meansfor the operation of compacting equipment whereby highly uniform,efficient, and controllable production of compacted material can beachieved.

It is a more specific object of this invention to provide improved screwfeed drive and control systems for feed screw drives in a briquettingmachine or the like whereby a uniform compacted product can be achieved.

These and other objects of this invention will appear hereinafter andfor purposes of illustration, but not of limitation, specificembodiments of the invention are shown in the accompanying drawings inwhich:

FIG. 1 is an elevational view ofa briquetting machine of the typesuitable for incorporation of the control system of this invention;

FIG. 2 is a schematic illustration of one form of control systemutilizing means for detecting the spacing between compacting rolls;

FIG. 3 is a schematic illustration of an alternative system utilizing atorque measuring arrangement;

FIG. 4 is a schematic illustration of a further alternative systemutilizing load measuring means;

FIG. 5 is a schematic illustration of a further alternative systemutilizing means for detecting the spacing between compacting rolls; and,

FIG. 6 is a schematic illustration of an electric motor drive andcontrol arrangement characterized by the features of this invention.

This invention is generally directed to a material compacting apparatusincluding opposed compacting rolls which are mounted for lateraldisplacement whereby the spacing between the rolls can vary in responseto variations in pressure during compacting of material between therolls. The hopper is provided for holding material to be compacted, anda feed screw is located within the hopper for feeding material betweenthe rolls.

The improvements of the invention are directed primarily to means formaintaining constant spacing between the rolls so that the compactedpowder will have uniform thickness. For example, in the case ofbriquetting machines, the briquet size and connecting web thickness iscontrolled and in the case of sheet, the thickness is controlled. Theconstant spacing is achieved by a system which determines changes inpressure during compacting, and which then acts to adjust the system tointroduce compensation whereby the variations can be substantiallyinstantaneously offset.

It has been found that the desired control can be ideally achieved in asystem which includes hydraulic drive means for the material feed screw.A variable or fixed displacement pump is utilized for deliveringhydraulic fluid to the hydraulic drive motor. Separate means areprovided for detecting changes in the pressure exerted by the compactingrolls on the material being compacted. When any variations are detectedthe detecting means develops a signal proportional to the degree ofvariation. This signal is in turn applied whereby the input to the drivemotor from the pump can be altered in accordance with the degree ofvariation. This will in turn affect the pressure applied by the feedscrew which introduces a compensating factor into the system. Inpractice, the great sensitivity of a system of the type describedresults in a substantially constant thickness of compacted product sinceany variation in pressure detected is immediately compensated for sothat there are no significant variations in the roll spacing.

It has also been found that electric motor drives and control systemscan be efficiently employed in conjunction with the material feed screwof briquetting and compacting machines. In such case, variations inpressure exerted by compacting rolls are detected and are preferablytransmitted to a process control means which applies its output to motorcontrol means whereby the electric motor for driving the feed screw canbe controlled to achieve uniformity of the compacted product.

FIG. 1 of the drawings illustrates a material compacting systemincluding a material feed hopper 12 and a feed screw 14 positionedwithin the hopper. The feed screw 14 is adapted to deliver material intothe nip of the briquetting rolls 16 and 17. Each of these briquettingrolls defines pockets 19 whereby the resulting compacted product willcomprise a plurality of briquets which can be separated for use.

The briquetting roll 16 is mounted for rotation within a displaceablebearing block 18. The briquetting roll 17 may be rotatable about astationary axis or, as illustrated, the roll may be mounted for rotationin a displaceable bearing block 20. Springs 22 are employed forresiliently maintaining the briquetting rolls in a proper spacedrelationship but permit yielding when the pressure between the rollsexceeds a certain level.

As long as this spaced relationship is maintained, the product issuingfrom between the rolls will be of uniform dimensions. In the event thatthere is a pressure change between the rolls and the material beingcompacted, then the displaceable rolls will move in opposition to thesprings 22 with the amount of movement depending upon the extent ofpressure build up. Such movement is relatively common in briquettingoperations since the material being compacted is, in the usual case,somewhat non-uniform and, therefore, there may be stages of operationwhere comparatively hard material is being briquetting whereby therewill be a tendency for the rollers to spread.

FIG. 2 illustrates one system which is suitable for controlling the feedscrew operation of a compacting system whereby a uniform product can beobtained. In this system, it will be understood that the rolls 16 and 17may be of various types, and in addition, various means may be employedfor mounting of the rolls. For example, hydraulic means may be appliedto one of both of the bearing blocks for purposes of resistingdisplacement of the bearing block while permitting such displacement inthe event variable pressure conditions develop during compacting.

The system of the invention involves the use of a hydraulic motor 26 fordriving the feed screw 14. Hydraulicsupply and return lines 28 and 30extend between the motor 26 and the variable displacement hydraulic pump32. The pump 32 includes a rotating shaft 34 connected to an electricdrive motor 36. A second electric motor 38 is connected to the pump, andthis motor serves to control the stroke of the pump to thereby controlthe power applied by the motor 26 to the feed screw 14.

The motor 38 is connected by means of lines 40 to controller 42. Thiscontroller is in turn connected through lines 44 to a roll positionsignal transducer 46. The signal transducer 46 may be of anyconventional design which will detect differences in spacing between therolls. When a variation is detected, a signal is transmitted to thecontroller 42 which applies a proportional signal to the motor 38.Depending upon the magnitude of the signal applied, the motor 38 willvary the stroke of the pump 32 for varying the driving power applied bythe motor 26 to the screw 14.

In the modification shown in FIG. 3, a differential pressure or constantflow signal transducer 50 is connected across the lines 28 and 30 whichextend between the motor 26 and pump 32. The signal transducer will,therefore, measure any changes in pressure in these hydraulic feedlines. The variations in pressure produce a signal which is directed tocontroller 42. The controller in turn controls the operation of motor 38whereby the stroke of the pump 32 can be varied.

It will be appreciated that with the system of FIG. 3, the pressure ofthe fluid in the lines 28 and 30 will change when the screw 14 driven bythe motor 26 is subjected to changing conditions. For example, if thematerial being fed between the compacting rolls increases in density,then the pressure exerted by the rolls on the material will increase.The system will tend to automatically seek relief by a displacement ofone or both of the compacting rolls.

The system of this invention avoids any significant displacement,however, by utilizing the signal developed in the transducer 50. In theexample given, the signal will result in a reduction in the drivepressure applied by the motor 26 to the screw 14. This reduction indrive pressure will compensate for the tendency toward pressure increasebetween the compacting rolls whereby the spacing between the rolls canremain constant.

FIG. 4 illustrates an additional modification of the invention wherein acurrent signal transducer 52 is associated with power supply line 54.This line is connected to the electric motor 56 which operates to drivethe compacting rolls.

The transducer 52 will generate signals and apply these to controller 42for purposes of operating the motor 38 associated with the pump 32. Thenature of the signals generated by the transducer 52 will depend uponthe power requirements of the motor 56. Whenever variations in thematerial being compacted result in changes in the pressure between therolls and material, these variations will affect the power requirementsof the electric motor 56. Such changes will in turn vary the conditionsin line 54 whereby a proportional signal can be developed by thetransducer 52. The system will then develop compensating changes in theoperation of the screw 14 whereby the conditions between the materialbeing compacted and the compacting rolls can be maintained constant.

The system shown in FIG. 5 provides an additional modification wherein afixed displacement pump 60 is provided for supplying the drive motor 26.In this system, a signal is applied by means of a roll position signaltransducer 62 of the type utilized in conjunctionwith the system of FIG.2. The signal transducer is connected to an electro-pneumatic signaltransducer 64 which is provided with power supply 66. A supply pressureregulator 68 is connected to the transducer 64, and to controller 70.The pneumatic signal output of the controller is, in turn, connected toa flow control valve 72 which may be a Taylor Precisor type withpneumatic operator or a Foxboro Valvactor type.

The flow control valve is connected in the line 74 between the pump 60and hydraulic motor 26. This valve will, therefore, control theoperation of the motor 26 since it will determine the flow of hydraulicfluid to the motor. This combination is possible with a fixeddisplacement pump since such pumps include means for diverting fluidwhereby the pumps dump hydraulic fluid depending upon the setting of acontrol valve included in the line connected to the output of the pump.It will be appreciated that the controller 70 and flow control valve 72may be operated by other signal producing systems such as thoseillustrated in FIGS. 3 and An adjustable by-pass valve could also beconnected to a controller and thereby serve to vary the effects of apump such as shown at 60. It will be appreciated that, in all of thesystems described above, the hydraulic control of the feed screw 14 isconnected to a compensating system. Thus, the invention calls forchanges in the displacement of an hydraulic pump 32 or 60 forcontrolling the power applied by the feed screw to the material beingcompacted FIG. 6 provides a schematic illustration of a constructionincorporating the features of the invention and employing an electricalsystem. The construction includes briquetting rolls 80 and a feed screw82. The motor shown at 85 may be, or example, (1) variable speed D. C.motors operated by conventional SCR and- /or thyratron or thyristorcircuitry or (2) variable speed eddy current clutch and motor driveswith clutch operated by conventional circuitry or (3) variable speed A.C. motor with motor speed controlled by varying electrical A. C.frequency using conventional circuitry. The variable speed control isshown at 86.

In each of the above, the commanding electrical signal to theconventional motor speed control circuitry is received from a processcontroller. This controller may be either electric or pneumatic and isshown in FIG. 6 at 90. An electric controller is preferred. The processcontroller senses the system operating condition by means of a signalreceived from the electrical transducer on the press drive motorelectrical leads, sensing the motor amperage, load or energy. Theprocess controller could also receive its system condition sensing froma roll gap position transducer shown in FIG. 2, item 46, or a sensingmethod sensing the torque or load on the feed screw motor, equivalent tothat shown in FIG. 3, item 50.

The controller 90 may be any suitable mechanism for operating asdescribed above whereby a signal will be transmitted to the motorcontrol 86 in accordance with variations detected in the operation ofroll drive motor 92. Thus, if the conditions of operation vary such thata greater or lesser demand is made on the motor 92, this will bemeasured by the signal transducer with the deviation being detected bythe process controller 90, the process controller then' applying acorrective signal to the motor control 86 for thereby affecting theoperation of the motor 85.

A VutroniK (trademark) deviation indicating control station of the typemanufactured by Honeywell, Inc. is a suitable process controller.Similar controllers are manufactured by Robert Shaw-Fulton, Fisher andPorter, General Electric, and others. Louis Allis and General Electricmanufacture motor controls of the type shown schematically at 86.

Roll gap detectors, electrical position transducers, and other means forproducing a differential signal may be employed, and reference is madeto the above discussion relative to hydraulic motor systems for theparticulars concerning applications of this nature. It will beappreciated, however, that the concepts of this invention are applicableto such systems as well as to other systems employing hydraulic orelectrical drive means in feed screw applications.

As indicated, various means may be employed for determining the signalsent by the controllers 42, 70 or 90 to the displacement motor 38, flowcontrol valve 72 or motor control 86. In all instances, however, theoperation of the controller is determined by any tendency towardvariation in pressure between the compacting rolls and the materialbeing compacted. Thus, it has been recognized that any tendency towardvariation in pressure in this area will affect various portions of thesystem with the effects being measurable. Specifically when the pressureapplied tends to increase due to a change in density of the material,this will tend to cause spreading of the compacting rolls, an increasein the power requirement for the screw drive motor, and also an increasein the power requirements for the roll drive motor. As shown, signaltransducers can be located for measuring the conditions which result dueto these tendencies. Furthermore, it has been recognized thatcompensation can be most efficiently introduced by controlling thestroke or displacement of a hydraulic motor or input to an electricmotor used for driving the feed screw.

It will be understood that various changes and modifications may be madein the above described systems which provide the characteristics of theinvention without departing from the spirit of the invention.

That which is claimed is:

1. In a material compacting apparatus including opposed compactingrolls, said rolls being mounted for lateral displacement relative toeach other whereby the spacing between the rolls will vary dependingupon the pressure exerted during compacting of material between therolls, and a feed screw for feeding material to said rolls, theimprovement comprising means for maintaining the spacing between saidrolls at a substantially constant distance comprising an electric motorfor driving said feed screw, a control for said motor, process controlmeans for varying the input applied by said control to said motor, meansfor detecting variations in the pressure exerted by said rolls on thematerial between the rolls, means for measuring the degree of variation,means for translating the degree of variation into a proportional outputand means for applying said proportional output to said process controlmeans for varying the input of said control to said motor to therebyvary the operation of said motor whereby the pressure applied by saidfeed screw will vary directly with changes in pressure between therolls.

2. An apparatus in accordance with claim 1 wherein the pressure exertedby said rolls on said material is determined by measuring the spacingbetween said rolls.

3. An apparatus in accordance with claim 1 wherein the pressure exertedby said rolls on the material is measured by determining the torqueapplied to said feed screw.

4. An apparatus in accordance with claim 1 including a motor for drivingsaid rolls, and wherein the pressure exerted by said rolls on saidmaterial is measured by determining the load on said motor.

5. An apparatus in accordance with claim 4 wherein the load on said rollmotor is determined by applying a current signal transducer to theelectrical supply for said roll motor, the output of said current signaltransducer being applied to means adapted to apply signals to saidcontroller.

1. In a material compacting apparatus including opposed compactingrolls, said rolls being mounted for lateral displacement relative toeach other whereby the spacing between the rolls will vary dependingupon the pressure exerted during compacting of material between therolls, and a feed screw for feeding material to said rolls, theImprovement comprising means for maintaining the spacing between saidrolls at a substantially constant distance comprising an electric motorfor driving said feed screw, a control for said motor, process controlmeans for varying the input applied by said control to said motor, meansfor detecting variations in the pressure exerted by said rolls on thematerial between the rolls, means for measuring the degree of variation,means for translating the degree of variation into a proportional outputand means for applying said proportional output to said process controlmeans for varying the input of said control to said motor to therebyvary the operation of said motor whereby the pressure applied by saidfeed screw will vary directly with changes in pressure between therolls.
 2. An apparatus in accordance with claim 1 wherein the pressureexerted by said rolls on said material is determined by measuring thespacing between said rolls.
 3. An apparatus in accordance with claim 1wherein the pressure exerted by said rolls on the material is measuredby determining the torque applied to said feed screw.
 4. An apparatus inaccordance with claim 1 including a motor for driving said rolls, andwherein the pressure exerted by said rolls on said material is measuredby determining the load on said motor.
 5. An apparatus in accordancewith claim 4 wherein the load on said roll motor is determined byapplying a current signal transducer to the electrical supply for saidroll motor, the output of said current signal transducer being appliedto means adapted to apply signals to said controller.